Deficits in Dynamic Balance and Hop Performance Following ACL Reconstruction Are Not Dependent on Meniscal Injury History.

Background: Athletes often exhibit persistent deficits in dynamic balance and hop performance in their involved limb following ACL reconstruction. However, it is unclear how meniscal injury history affects inter-limb asymmetry. Purpose: The purpose of this study was to compare inter-limb asymmetry in dynamic balance and hop performance in athletes with and without a history of concomitant meniscal injury. Study Design: Cross-sectional study. Methods: Dynamic balance and hop test data were analyzed for 34 adolescent athletes who had undergone ACL reconstruction; 19 athletes had sustained an isolated ACL tear, while 15 had sustained an ACL tear along with a meniscus injury. Athletes who had sustained a meniscus injury were sub-divided into those who underwent a meniscal repair (n = 9) versus a partial meniscectomy (n = 6). Dynamic balance was assessed using the Y-Balance Test, while hop performance was assessed using the single and triple hop tests. Data were recorded at the time of return-to-sport testing (5-11 months post-surgery). For each variable, mixed-model analysis of variance, with a between-subjects factor of group (isolated ACL tear, meniscal repair, partial meniscectomy) and a within-subjects factor of limb (involved, uninvolved), was conducted. Results: The groups exhibited similar degrees of inter-limb asymmetry in dynamic balance and hop test performance, as there was not a group-by-limb interaction effect for the Y-Balance Test distances (p ≥ 0.43) or hop test distances (p ≥ 0.96). However, there was a main effect of limb for the anterior and posteromedial Y-Balance Test distances and the single and triple hop test distances (p ≤ 0.004). For each variable, performance was worse for the involved limb, compared to the uninvolved limb. Conclusion: It appears that deficits in dynamic balance and hop performance among adolescent athletes who have undergone ACL reconstruction are not dependent on meniscal injury/surgery history. Level of Evidence: 3.

The effects of incremental changes in rucksack load on lower extremity joint Kinetic patterns during ruck marching.

Injuries are often attributed to ruck marching. Therefore, it is important to examine how load carriage influences gait mechanics. The purpose of this study was to examine how subtle changes in rucksack load influence joint torque patterns during marching. Fourteen Army ROTC cadets marched with light, moderate, and heavy rucksack loads. Kinetic and kinematic data were recorded via an instrumented treadmill and motion capture system and principal component analysis was used to analyse the joint torque waveforms. Cadets exhibited moderate-large increases in knee extension torques during early stance (effect sizes ≥0.45) and small-moderate increases in ankle plantarflexion torques during push off (effect sizes ≥0.23) with each incremental increase in rucksack load. The lighter load also resulted in lower hip extension torques during early stance and flexion torques during late stance, vs. the moderate and heavier loads (effect sizes ≥0.23). It appears that subtle changes in rucksack load influence marching mechanics. Practitioner Summary: The purpose of this study was to examine how relatively subtle changes in rucksack load influence marching mechanics. Army ROTC cadets marched with relatively light, moderate, and heavy rucksack loads. Our results indicate that even subtle changes in rucksack load influence joint torque patterns of the hip, knee, and ankle. Abbreviations: ROTC: reserve officer training corps; RoF: rating-of-fatigue; PC: principal component; ICC: intraclass correlation coefficient; ES: effect size.

Differences in neuromuscular strategies between landing and cutting tasks in female basketball and soccer athletes.

CONTEXT: High school female athletes are most likely to sustain a serious knee injury during soccer or basketball, 2 sports that often involve a rapid deceleration before a change of direction or while landing from a jump. OBJECTIVE: To determine if female high school basketball and soccer players show neuromuscular differences during landing and cutting tasks and to examine neuromuscular differences between tasks and between dominant and nondominant sides. DESIGN: A 3-way mixed factorial design investigating the effects of sport (basketball, soccer), task (jumping, cutting), and side (dominant, nondominant). SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Thirty high school female athletes who listed either basketball or soccer as their only sport of participation (basketball: n = 15, age = 15.1 +/- 1.7 years, experience = 6.9 +/- 2.2 years, height = 165.3 +/- 7.9 cm, mass = 61.8 +/- 9.3 kg; soccer: n = 15, age = 14.8 +/- 0.8 years, experience = 8.8 +/- 2.5 years, height = 161.8 +/- 4.1 cm, mass = 54.6 +/- 7.6 kg). MAIN OUTCOME MEASURE(S): Ground reaction forces, stance time, valgus angles, and valgus moments were assessed during (1) a drop vertical jump with an immediate maximal vertical jump and (2) an immediate side-step cut at a 45 degrees angle. RESULTS: Basketball athletes had greater ground reaction forces (P < .001) and decreased stance time (P < .001) during the drop vertical jump, whereas soccer players had greater ground reaction forces (P <.001) and decreased stance time (P < .001) during the cut. Subjects in both sports had greater valgus angles (initial contact and maximum, P = .02 and P = .012, respectively) during cutting than during the drop vertical jump. Greater valgus moments (P = .006) were noted on the dominant side during cutting. CONCLUSIONS: Our subjects demonstrated differences in ground reaction forces and stance times during 2 movements associated with noncontact anterior cruciate ligament injuries. Knee valgus moment and angle were significantly influenced by the type of movement performed. Sport-specific neuromuscular training may be warranted, with basketball players focusing on jumping and landing and soccer players focusing on unanticipated cutting maneuvers.

Gender differences in frontal and sagittal plane biomechanics during drop landings.

PURPOSE: To determine gender differences in lower-extremity joint kinematics and kinetics between age- and skill-matched recreational athletes. METHODS: Inverse dynamic solutions estimated the lower-extremity flexion-extension and varus-valgus kinematics and kinetics for 15 females and 15 males performing a 60-cm drop landing. A mixed model, repeated measures analysis of variance (gender (*) joint) was performed on select kinematic and kinetic variables. RESULTS: Peak hip and knee flexion and ankle dorsiflexion angles were greater in females in the sagittal plane (group effect, P < 0.02). Females exhibited greater frontal plane motion (group (*) joint, P = 0.02). Differences were attributed to greater peak knee valgus and peak ankle pronation angles (post hoc tests, P = 0.00). Females exhibited a greater range of motion (ROM) in the sagittal plane (group main effect, P = 0.02) and the frontal plane (group (*) joint, P = 0.01). Differences were attributed to the greater knee varus-valgus ROM, ankle dorsiflexion, and pronation ROM (post hoc tests). Ground reaction forces were different between groups (group (*) direction, P = 0.05). Females exhibited greater peak vertical and posterior (A/P) force than males (post hoc tests). Females exhibited different knee moment profiles (Group main effect, P = 0.01). These differences were attributed to a reduced varus moment in females (post hoc tests). CONCLUSION: The majority of the differences in kinematic and kinetic variables between male and female recreational athletes during landing were observed in the frontal plane not in the sagittal plane. Specifically, females generated a smaller internal knee varus moment at the time of peak valgus knee angulation.